%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-2-16 on page II-140 in "Multiple alignments: \protect \nxLenv  {align} and \protect \nxLenv  {flalign}".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3examargin}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{183.0pt}

%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands

\begin{document}
\renewcommand\minalignsep{30pt}
\begin{align}
  x      &= y      && \text{by hypothesis} \\
      x' &= y'     && \text{by definition} \\
  x + x' &= y + y' && \text{by Axiom 1}
\end{align}
\renewcommand\minalignsep{10pt}
\end{document}
